/*
 * Copyright (C) 2017 Apple Inc. All rights reserved.
 * Copyright (C) 2017 Metrological Group B.V.
 * Copyright (C) 2017 Igalia S.L.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
 * THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "config.h"
#include "CryptoAlgorithmECDH.h"

#if ENABLE(SUBTLE_CRYPTO)

#include "CryptoKeyEC.h"
#include "ScriptExecutionContext.h"
#include <pal/crypto/gcrypt/Handle.h>
#include <pal/crypto/gcrypt/Utilities.h>

namespace WebCore {

static std::optional<Vector<uint8_t>> gcryptDerive(gcry_sexp_t baseKeySexp, gcry_sexp_t publicKeySexp)
{
    // First, retrieve private key data, which is roughly of the following form:
    // (private-key
    //   (ecc
    //     ...
    //     (d ...)))
    PAL::GCrypt::Handle<gcry_sexp_t> dataSexp;
    {
        PAL::GCrypt::Handle<gcry_sexp_t> dSexp(gcry_sexp_find_token(baseKeySexp, "d", 0));
        if (!dSexp)
            return std::nullopt;

        size_t dataLength = 0;
        const char* data = gcry_sexp_nth_data(dSexp, 1, &dataLength);
        if (!data)
            return std::nullopt;

        gcry_sexp_build(&dataSexp, nullptr, "(data(flags raw)(value %b))", dataLength, data);
        if (!dataSexp)
            return std::nullopt;
    }

    // Encrypt the data s-expression with the public key.
    PAL::GCrypt::Handle<gcry_sexp_t> cipherSexp;
    gcry_error_t error = gcry_pk_encrypt(&cipherSexp, dataSexp, publicKeySexp);
    if (error != GPG_ERR_NO_ERROR) {
        PAL::GCrypt::logError(error);
        return std::nullopt;
    }

    // Retrieve the shared point value from the generated s-expression, which is of the following form:
    // (enc-val
    //   (ecdh
    //     (s ...)
    //     (e ...)))
    Vector<uint8_t> output;
    {
        PAL::GCrypt::Handle<gcry_sexp_t> sSexp(gcry_sexp_find_token(cipherSexp, "s", 0));
        if (!sSexp)
            return std::nullopt;

        PAL::GCrypt::Handle<gcry_mpi_t> sMPI(gcry_sexp_nth_mpi(sSexp, 1, GCRYMPI_FMT_USG));
        if (!sMPI)
            return std::nullopt;

        PAL::GCrypt::Handle<gcry_mpi_point_t> point(gcry_mpi_point_new(0));
        if (!point)
            return std::nullopt;

        error = gcry_mpi_ec_decode_point(point, sMPI, nullptr);
        if (error != GPG_ERR_NO_ERROR)
            return std::nullopt;

        PAL::GCrypt::Handle<gcry_mpi_t> xMPI(gcry_mpi_new(0));
        if (!xMPI)
            return std::nullopt;

        // We're only interested in the x-coordinate.
        gcry_mpi_point_snatch_get(xMPI, nullptr, nullptr, point.release());

        size_t dataLength = 0;
        error = gcry_mpi_print(GCRYMPI_FMT_USG, nullptr, 0, &dataLength, xMPI);
        if (error != GPG_ERR_NO_ERROR) {
            PAL::GCrypt::logError(error);
            return std::nullopt;
        }

        output.resize(dataLength);
        error = gcry_mpi_print(GCRYMPI_FMT_USG, output.data(), output.size(), nullptr, xMPI);
        if (error != GPG_ERR_NO_ERROR) {
            PAL::GCrypt::logError(error);
            return std::nullopt;
        }
    }

    return output;
}

void CryptoAlgorithmECDH::platformDeriveBits(Ref<CryptoKey>&& baseKey, Ref<CryptoKey>&& publicKey, size_t length, Callback&& callback, ScriptExecutionContext& context, WorkQueue& workQueue)
{
    context.ref();
    workQueue.dispatch(
        [baseKey = WTFMove(baseKey), publicKey = WTFMove(publicKey), length, callback = WTFMove(callback), &context]() mutable {
            auto& ecBaseKey = downcast<CryptoKeyEC>(baseKey.get());
            auto& ecPublicKey = downcast<CryptoKeyEC>(publicKey.get());

            auto output = gcryptDerive(ecBaseKey.platformKey(), ecPublicKey.platformKey());
            context.postTask(
                [output = WTFMove(output), length, callback = WTFMove(callback)](ScriptExecutionContext& context) mutable {
                    callback(WTFMove(output), length);
                    context.deref();
                });
        });
}

} // namespace WebCore

#endif // ENABLE(SUBTLE_CRYPTO)
